Suppose the pressure of 20 g of an ideal monatomic gas is tripled while its volume is halved.What happens to the internal energy of the gas?
A)It stays the same,as the described changes do not involve internal energy.
B)It increases.
C)It decreases.
D)This depends on the molecular weight of the gas involved,thus this is indeterminate.

Question

Quizplus · Accepted Answer

When the pressure is tripled and the volume is halved, the gas undergoes an adiabatic compression. During this process, the internal energy of the gas increases. This is because the work done on the gas (by decreasing its volume) is positive, and according to the first law of thermodynamics, the change in internal energy is equal to the heat added to the system minus the work done by the system. Since this is an adiabatic process, there is no heat added to the system, and thus the change in internal energy is equal to the work done on the system, which is positive. Therefore, the answer is (B) it increases.

Suppose the Pressure of 20 G of an Ideal Monatomic